1. Field of the Invention
The present invention relates to an optical card having guide patterns used to position a light beam to a target line of a plurality of information lines which form tracks and an optical card recording/reproducing apparatus for recording information to and/or reproducing information from the optical card.
In recent years, an optical card recording/reproducing apparatus which is capable of optically performing a recording and reproduction operation by irradiating a light beam instead of using a magnetic head have come to be widely used. For optical recording mediums used in such optical card recording/reproducing apparatus, recording mediums in the form of disks (hereinafter referred to as optical disks) and cards (hereinafter referred to as optical cards) are commonly used.
An optical card has the same size and shape as a credit card, and can be carried easily. It features a large storage capacity and low cost optical cards are expected to be information recording carriers of the next generation, and various types have been proposed.
Referring to the accompanying drawings, the prior art will now be explained. An optical card 1' shown in FIG. 1 is disclosed, for example, in Japanese utility Model Publication No. 63-145669.
In such optical card 1', information is recorded as high or low reflectance (sometimes the high portion is represented in white and the low portion is in black), and optically reproduced. This information is recorded and/or reproduced in a unit called a track 1-3. A plurality of tracks 1-3 in bands or lines are arranged parallel to one another, and thus forming one card.
In the prior art shown in FIG. 1, ID areas 1-2a and 1-2b in which track Nos. for identifying the tracks are written, are placed at both ends of the tracks 1-3. In the remaining portions, data area 1-1 to which data is previously recorded or recorded additionally is formed.
Specific recognition patterns common to all tracks are prerecorded in the ID areas 1-2a and 1-2b in addition to the track numbers in order for a track number to be recognized, making it easy to seek a target track.
FIG. 2 shows in detail the tracks in area A of FIG. 1 surrounded by the dotted line. In the tracks 1-3, clock patterns 1-5 are prerecorded. The clock patterns 1-5 which extend parallel to the tracks, having a high and a low reflectance, are prerecorded in clock line area 1-4 in the central portion in the direction of the track width and are used to generate a tracking error signal and a focus error signal.
In the data area 1-1, 16 information lines are formed so that data of 8 bits can be recorded in the direction of the track width, at both sides of the clock line area 1-4 in the center (a total of 16 bits can be recorded).
The clock patterns 1-5 formed in the clock line area 1-4 in the center serve as guides used to detect that the central position of a track has been detected (used to generate a tracking error signal). White and black patterns are formed so that clocks, which become synchronization signals when pits recorded in each information line of the data area 1-1 are reproduced, can be generated.
In ID area 1-2a, reference numerals 1-6a to 1-6h denote specific recognition patterns common to the tracks, and reference numerals 1-71 to 1-78 denote patterns indicating track numbers. A track number 1-7 and a recognition pattern 1-6 in the ID area 1-2a are detected during the seek operation. Data of 16 bits long in data area 1-1a is read at one time during the recording and/or reproduction operation. Thus, the speed of the reading operation is increased.
FIG. 3 shows an arrangement similar to the optical pickup disclosed in Japanese Patent Laid-Open No. 63-153727. Light beams from a light source 3 (e.g., an led) are formed into substantially parallel light beams by a collimator lens 4. The light beams transmitted through a half prism 5 are condensed by an object lens 6, and projected onto the recording surface of the optical card 1.
As a result, a light spot illuminating an area wide enough to cover one track is formed. The reflected light beams thereof are condensed by the object lens 6, reflected by the half prism 5, are made to pass through an image forming lens 7, and received by a photodetector 8.
FIG. 4 shows the photoreceptive surface of the photodetector 8.
The image on tracks 1-3 shown in FIG. 2 is projected onto the photoreceptive surface of the photodetector 8 so as to cover one track, and a detection signal is output.
The photodetector 8 comprises 16 photoreceptive areas 8-A1 to 8-A16 for reading data disposed in correspondence with data recording positions for 16 bits in the direction of the track width, five pairs of photoreceptive areas 8-B1 to B10 for generating clocks, disposed spaced apart in the track direction so as to receive the image of the clock pattern 1-5, and four pairs of photoreceptive areas 8-C1 to 8-C4 and 8-D1 to 8-D4 for detecting servo signals, disposed spaced apart in the track direction so as to receive the image of both edge portions of the clock pattern 1-5 in the track direction.
In the photodetector of FIG. 4, a focus error signal (FE) is obtained on the basis of the sum of the outputs of the photoreceptive areas 8-C1 to 8-C4 for detecting servo signals on the outside, and the outputs of the photoreceptive areas 8-D1 to 8-D4, for detecting servo signals on the inside. A tracking error signal (TE) is obtained on the basis of the difference between the sum of the outputs of the photoreceptive areas 8-D1 and 8-D3, for detecting servo signals, and the sum of the outputs of the photoreceptive areas 8-D2 and 8-D4, for detecting servo signals.
A clock signal is obtained on the basis of the difference between the sum of the outputs of the photoreceptive areas 8-B1, 8-B3, 8-B5, 8-B7 and 8-B9, each of which forms one half of the pair of areas for generating clocks, and the sum of the outputs of the photoreceptive areas 8-B2, 8-B4, 8-B6, 8-B8 and 8-B10, each of which forms the other of the pair. In synchronization with this clock signal, 16 bits of data are read at one time on the basis of the outputs of the photoreceptive areas 8-A1 to 8-A16.
FIG. 5 shows a tracking error signal (TE) when an optical pickup is moved in a forward/backward direction, and a specific recognition pattern matching signal common to each track, in the seek direction (in the direction of the track width) in a condition where the tracking servo system is open. The track number is input on the basis of the zero cross signal of the track error signal plus the recognition pattern matching signal to determine whether the target track is detected.
However, when recording information by using an optical card format of the prior art, a track number during the seek operation is input when the zero cross signal of the track error signal matches a recognition pattern common to each track and a target track is detected. Therefore, when a recording beam is projected onto a desired information line within 16 lines of a data area in one track and information is recorded, even though positioning among tracks is easy, positioning to a desired information line in the direction of the track width within the track is difficult.
In the example in FIG. 5, although a recognition pattern matching signal is output at the central positions of tracks N and N-1, the matching signal output becomes indefinite because of a combination of patterns indicating track numbers among tracks.
That is, positioning for each track in a clock pattern position in the center of each track is easy, but positioning on a information line is difficult. Since a reproducing apparatus used exclusively for reproducing efficiently the information recorded on an optical card is used in the prior art, this degree of positioning accuracy is sufficient for an optical card recorded by such a format. However, to record information, a desired information line must be accessed, and positioning at an arbitrary information line within a track is required.
As shown in FIG. 5, when the information line is traversed at a position other than a clock pattern position, in the center of each track, a signal similar to the tracking error signal is output.
This signal cannot be used for positioning on a desired information line because the signal changes in response to the pattern of the track recognition number (this number is common to all tracks) and the track number.
In Japanese Patent Laid-Open No. 63-153727, one semiconductor laser is used as a recording light source, information is written on a plurality of information lines within one track of the optical card by scanning a recording beam from the semiconductor laser in the direction of the track width by causing a mirror to be rotated by a bimorph or the like. Thus, the recording density of one track is increased.
In Japanese Patent Laid-Open No. 62-279523, a recording beam is deflected by causing a recording element itself (a semiconductor laser) to move in the direction of the track width so that information is written on a plurality of information lines of one track.
In the above-described two examples of the prior art, reliable positioning on an information line is difficult. In other words, positioning of a recording beam reference is performed on the basis of the light reflected from a clock pattern position, in the center of the track, and a mirror is rotated from this reference position according to the information line. Thus, positioning to the information line is performed. In this case, the function for reliably positioning on an information line is fairly inaccurate and an erroneous irradiation of light beams to a neighboring information line may occur since whether or not light beams are reliably set on a target information line cannot be detected or determined because positioning is not performed by directly receiving light reflected from the information line portion.